John Calvin Commentary Psalms 103:8

"Jehovah is merciful and gracious, Slow to anger, and abundant in lovingkindness." — Psalms 103:8 (ASV)

Jehovah is merciful and gracious. David seems to allude to the exclamation of Moses, recorded in Exodus 34:6, where the nature of God, revealed in a remarkable way, is more clearly described than in other places. When Moses was allowed a closer view of the Divine glory than was usually obtained, he exclaimed upon seeing it, “O God! merciful and gracious, forgiving iniquity, slow to wrath, and abundant in goodness.”

Therefore, since Moses concisely expressed in that passage all that is important for us to know about the Divine character, David aptly applies these terms, by which God is described there, to his present purpose. His design is to ascribe entirely to God's goodness the fact that the Israelites, who by their own wickedness repeatedly forfeited their relationship with Him as His adopted people, nevertheless remained in that relationship.

Furthermore, we must understand in general that the true knowledge of God corresponds to what faith discovers in the written Word. For it is not His will that we should search into His secret essence, except insofar as He makes Himself known to us—a point deserving our special attention.

We see that whenever God is mentioned, people's minds are perversely carried away to cold speculations, fixing their attention on things that offer them no benefit. Meanwhile, they neglect those manifestations of His perfections that are evident to us and provide a vivid reflection of His character.

To whatever subjects people apply their minds, there is none from which they will derive greater advantage than from continual meditation on His wisdom, goodness, righteousness, and mercy. Especially, the knowledge of His goodness is suited both to build up our faith and to magnify His praises. Accordingly, Paul, in Ephesians 3:18, declares that our height, length, breadth, and depth, consists in knowing the unspeakable riches of grace, which have been manifested to us in Christ.

This is also the reason why David, copying from Moses, magnifies God's mercy with a variety of terms. In the first place, since we have no worse fault than that devilish arrogance which robs God of His due praise—and which is yet so deeply rooted in us that it cannot be easily eradicated—God rises up and, so that He may bring to nothing the heaven-daring presumption of the flesh, asserts in lofty terms His own mercy, by which alone we stand.

Again, when we should rely upon the grace of God, our minds tremble or waver, and we find nothing more difficult than acknowledging that He is merciful to us. David, to address and overcome this doubting state of mind, following the example of Moses, employs these synonymous terms: first, that God is merciful; secondly, that He is gracious; thirdly, that He patiently and compassionately bears with the sins of people; and, lastly, that He is abundant in mercy and goodness.